The present invention relates to a dispersion composition and a method for producing the same. More particularly, it relates to a dispersion composition which can be utilized in the technical fields where a particulate material insoluble in organic solvent is dispersed and used, for example, the field of paint, printing ink, liquid developer (wet toner) or ink jet ink where a pigment or a dye as a particulate material is dispersed and utilized, the field where a medicine as a particulate material is dispersed and utilized, and the field where a catalyst or a polymerization initiator as a particulate material is dispersed and utilized, and to a method for producing the same. The present invention further relates to a dispersion composition utilizable also in the field of coloring materials comprising a polymeric compound in which a particulate material is included by drying, such as dry toners, powdered paints, and plastics, and to a method for producing the same.
Hitherto, in the field of utilizing pigments or dyes which are particulate materials insoluble in organic solvents, a fine dispersion of particles has been made resulting in improved storage stability. For example, British Patent No. 2001083 discloses the use of a specific polyester amine as a pigment dispersant in paints or inks.
Furthermore, JP-A-8-30040 discloses a liquid developer prepared by dispersing in a non-aqueous solvent an urethane-based microencapsulated colored resin particle containing a pigment or a dye.
Moreover, JP-A-3-160464 discloses a solid self-dispersion type coloring material comprising a mixture of a pigment or a dye and a self-dispersion type graft polymer which forms particles upon self-dispersing in a high insulation carrier liquid, and mentions use of silicone-based graft polymers.
However, in the dispersion compositions using general dispersion stabilizers and pigment dispersants disclosed in the above British Patent No. 2001083, the type of organic solvent or pigment used is limited. Moreover, stabilization of the dispersion has been attempted by steric repulsion of the resins, however since the amount of electric charge generated at the surface of the pigment is small, in the case of dilute pigment dispersion, sedimentation occurs when stored for a long time and thus it lacks dispersion stability.
Furthermore, the solid self-dispersion type coloring material using urethane-based microencapsulated colored resin particles or self-dispersion type graft copolymers have the problem of sedimentation in long-term storage when they are used for liquid developers or ink jet inks because of their large dispersion particle diameter.
Moreover, the polymer toners have a large particle diameter because they are obtained by dispersing a reactive silicone monomer, an isocyanate and a coloring material and then polymerizing them, and the silicone-containing polymer used for the improvement of dispersibility dissolves in the organic solvent in the ink to cause sedimentation of toner particles in the ink.
Accordingly, the object of the present invention is to provide a dispersion composition which is enhanced in dispersion stability of a particulate material, solves the problem of sedimentation, expands the kind of usable organic solvent or insoluble particulate materials and is wide in use, especially useful for liquid developers or ink jet inks which utilize the electrostatic force.
The above object can be attained by a dispersion composition comprising a particulate material dispersed in an organic solvent where a graft copolymer in which the graft chain comprises a polysiloxane and an alkylene group (hereinafter referred to as xe2x80x9cgraft copolymer Axe2x80x9d) is adsorbed to at least a part of the outer surface of said particulate material.
According to the research conducted by the inventors, it has been found that by adsorbing the graft copolymer A to at least a part of the outer surface of a particulate material, the particulate material can be made finer and electric charge can be generated at the surface of the particulate material, whereby steric repulsive force between the particulate materials per se is enhanced, and sedimentation of the particulate material is inhibited and dispersion stability is enhanced.
The graft copolymer A in the present invention is a copolymer of such a type that a branch (graft chain) of a homopolymer grows at a backbone (main chain) of another homopolymer. This graft chain is composed of a polysiloxane and an alkylene group. The polysiloxane means a chain of siloxane bond (xe2x80x94Sixe2x80x94Oxe2x80x94). By bonding the polysiloxane through the alkylene group, the portion of polysiloxane is sufficiently extended for an organic solvent, especially, an organic solvent having a resistivity of not less than 109 xcexa9xc2x7cm (e.g., aliphatic hydrocarbons or silicone solvents), and the particulate material can be finely and stably kept. Furthermore, since the graft copolymer A is adsorbed to the surface of pigment so as to cover the particulate material, electric charge can be generated.
Moreover, the dispersion composition of the present invention can be produced by mixing a dispersion comprising a particulate material dispersed using a graft copolymer having a particle diameter of 0.01-1 xcexcm in an organic solvent in which said graft copolymer is soluble with an organic solvent in which said graft copolymer is insoluble, thereby precipitating the graft copolymer to adsorb the graft copolymer to at least a part of the outer surface of the particulate material.
In the dispersion composition of the present invention, it is essential that the graft chain bonded to the graft backbone (main chain) in the graft copolymer A adsorbed to the particulate material comprises a polysiloxane and an alkylene group. More preferred is a structure where the polysiloxane is bonded to the main chain through the alkylene group. The structure of the graft chain comprising a polysiloxane and an alkylene group is represented by the following formula. 
X: A linkage group containing at least one of urethane group, amide group and ester group.
R1: An alkylene group of 1-18 carbon atoms.
R2: An alkyl group of 1-4 carbon atoms.
R3: H or CH3 
n : An integer of 5-200.
The alkylene group is not particularly limited as far as the carbon number is 1 or more, but an alkylene group of 1-18 carbon atoms is preferred. An alkylene group of more than 18 carbon atoms is not preferred since the solubility of the graft polymer increases and the self-dispersion becomes difficult. An alkylene group of 1-12 carbon atoms is especially preferred. The polysiloxane is preferably polydimethylsiloxane and the molecular weight thereof is preferably 370-15000. Bonding of the alkylene group in the graft chain to the graft backbone (main chain) is conducted through an ester group, an amide group, an urethane group or the like. The ester group is especially preferred which can be simply obtained.
In the case of the general graft copolymers having a graft chain comprising only a polysiloxane shown in JP-A-6-160464, there is no extension of the graft portion in the organic solvent, and dispersion particle diameter of the particulate material increases and it sediments when used for preparation of jet ink and the like.
In the dispersion composition of the present invention, it is essential that the graft copolymer A adsorbed to the particulate material has a particle diameter of 0.01-1 xcexcim and self-disperses in an organic solvent. If the particle diameter is more than 1 xcexcm, it becomes difficult to improve the dispersion stability of the particulate material, and if it is less than 0.01 xcexcm, the particulate material cannot be covered. More preferred range of the particle diameter is 0.015-0.5 xcexcm, and further preferred is 0.015-0.25 xcexcm. For obtaining the finer and very stable dispersion composition, the particle diameter is preferably 0.015-0.09 xcexcm.
The term xe2x80x9cself-dispersexe2x80x9d employed in the present specification means that the graft copolymer A does not dissolve in an organic solvent and only the graft copolymer A by itself disperses. For example, it means a phenomenon that after the graft copolymer A is dissolved in an organic solvent which dissolves the graft copolymer A, when this solution is mixed with an organic solvent which does not dissolve the graft copolymer A, the graft copolymer does not form large masses and disperses in the form of particles. The self-dispersion disclosed in JP-A-3-160464 shows one which occurs only by adding a solid graft copolymer to a carrier liquid and this is a phenomenon different from the self-dispersion in the present invention. Moreover, the graft polymer in the present invention which is made solid does not self-disperse only by adding it to a carrier liquid. The average particle diameter of the graft copolymer A can be measured by a general known particle size distribution meter such as a laser type particle size distribution meter or a centrifugal sedimentation type particle size distribution meter.
Furthermore, the graft copolymer A preferably has a polar group for finely dispersing the particulate material and giving electric charge to the particulate material to improve the dispersion stability. The polar groups suitable for such purpose are not limited and include basic groups, acidic groups, hydroxyl group, and the like. Especially, acidic group and hydroxyl group are preferred for finely dispersing the particulate material and for performing crosslinking reaction. As basic groups, there are no special limitations, and mention may be made of primary, secondary, tertiary and quaternary amino groups. As acidic groups, there are no special limitations, and mention may be made of carboxyl group, sulfonic acid group and phosphonic acid group. Carboxyl group of low acid strength is especially preferred since agglomeration of the dispersion composition hardly occurs and from the point of reaction rate of the crosslinking reaction.
Acid value of the graft copolymer A is preferably in the range of 5-200 KOH mg/g. If the acid value is less than 5 KOH mg/g, affinity with the particulate material is weak and fine dispersion composition cannot be obtained or electric charge of the particulate material becomes small. If it exceeds 200 KOH mg/g, acid strength of the graft copolymer A increases and extension of the graft copolymer A in the organic solvent becomes small, and, thus, adsorption to the particulate material becomes difficult.
Hydroxyl value of the graft copolymer A is preferably in the range of 5-200 KOH mg/g. If the hydroxyl value is less than 5 KOH mg/g, affinity with the particulate material is weak and fine dispersion composition cannot be obtained or electric charge of the particulate material becomes small. If it exceeds 200 KOH mg/g, polarity of the graft copolymer A increases and extension of the graft copolymer A in the organic solvent becomes small, and, thus, adsorption to the particulate becomes difficult. Amine value of the graft copolymer A is preferably in the range of 5-200 KOH mg/g. If the amine value is less than 5 KOH mg/g, affinity with the particulate material is weak and fine dispersion composition cannot be obtained or electric charge of the particulate material becomes small. If it exceeds 200 KOH mg/g, polarity of the graft copolymer A increases and extension of the graft copolymer A in the organic solvent becomes small, and, thus, adsorption to the particulate becomes difficult.
Number-average molecular weight of the graft copolymer A is preferably in the range of 1000-50000. If the number-average molecular weight is less than 1000, it becomes difficult to finely disperse the particulate material, and sedimentation of the particulate material is caused. If it exceeds 50000, dissolution in the solvent becomes difficult to cause increase of viscosity of the dispersion composition. More preferred range is 3000-30000.
Particle size distribution is preferably in the range of 0.01-1.0 xcexcm, and 0.01-0.5 xcexcm is more preferred from the point of sedimentation of the particulate material. Further preferred range is 0.01-0.25 xcexcm. The particle size distribution of the particulate material can be controlled to the range of 0.01-1.0 xcexcm, for example, by the method of dry grinding the particulate material together with grinding medium such as balls by a ball mill, the method of wet grinding the particulate material together with grinding medium such as balls in a solvent by a ball mill, and the method of dissolving the particulate material in a specific solvent and then precipitating it (for example, by dissolving the particulate material in sulfuric acid and thereafter precipitating it with addition of water or by adding the solution to water).
The particulate material to which the graft copolymer A is adsorbed in the dispersion composition of the present invention is not limited, but preferably has an electric charge from the point of dispersion stability. For example, as the electric charge of the particulate material, preferred is not less than 10 mV, more preferred is not less than 15 mV in absolute value of xcex6 potential.
The graft copolymer A keeps the adsorptivity to the particulate material and extension of resin into the organic solvent by having such a structure that the main backbone adsorbed to the particulate material and the portion having affinity for the organic solvent are bonded to polysiloxane through the main backbone and alkylene group. There is no problem to use amphoteric polymer compounds having both the acidic group and the basic group.
The method for producing the graft copolymer A is not limited. The graft copolymer A can be obtained by reacting a silicone-based macromonomer comprising polysiloxane and alkylene group for graft chain as an essential component with other polymerizable monomer for main chain in a non-reactive solvent in the presence or absence of a catalyst. Especially preferably, the silicone-based macro-monomer is copolymerized with a monomer having polar group for main chain. Another preferred method comprises synthesizing an acrylic polymer having a reactive group and then reacting it with a reactive silicone to perform grafting. In the production of the graft copolymer A of the present invention, the monomers for main chain may be used alone or in combination of two or more.
In the present invention, as the silicone-based macro-monomers for graft chain comprising polysiloxane and alkylene group, mention may be made of those represented by the following formula:
xe2x80x83Rxe2x80x3(Si(CH3)2O)nSi(CH3)2xe2x80x94Rxe2x80x94Xxe2x80x94CRxe2x80x2xe2x95x90CH2
wherein R is an alkylene group of 1-18 carbon atoms, Rxe2x80x2 is CH3 or H, Rxe2x80x3 is an alkyl group of 1-4 carbon atoms, n is an integer of 5-200, X is a linkage group containing at least one of urethane group, amido group and ester group.
Specifically, there may be used the following commercially available products manufactured by Shin-Etsu Chemical Co., Ltd.:
X-22-174DX: CH3(CH2)3xe2x80x94(Si(CH3)2O)61xe2x80x94Si(CH3)2xe2x80x94C3H6xe2x80x94OCOxe2x80x94CCH3xe2x95x90CH2 
X-24-8201: CH3(CH2)3xe2x80x94(Si(CH3)2O)151xe2x80x94Si(CH3)2xe2x80x94C3H6xe2x80x94OCOxe2x80x94CCH3xe2x95x90CH2 
X-22-2426: CH3xe2x80x94(Si(CH3)2O)26xe2x80x94Si(CH3)2xe2x80x94C3H6xe2x80x94OCOxe2x80x94CCH3xe2x95x90CH2 
In addition, there may be used CH3xe2x80x94(Si( CH3)2O)nxe2x80x94Si(CH3)2xe2x80x94C3H6xe2x80x94CHOHxe2x80x94CH2OCOxe2x80x94CCH3xe2x95x90CH2, CH3xe2x80x94(Si( CH3)2O)nxe2x80x94Si(CH3 )2xe2x80x94C3H6xe2x80x94NHCOxe2x80x94CCH3xe2x95x90CH2, CH3xe2x80x94(Si(CH3 )2O)nxe2x80x94Si( CH3)2xe2x80x94C3H6xe2x80x94OC2H4OCONH(CH2)6NHCOOCOxe2x80x94CCH3xe2x95x90CH2, etc. which are synthesized by the processes known to one skilled in the art.
Among the polar group-containing acrylic monomers used for forming the graft backbone (main chain) of the graft copolymer A, examples of the monomers having an acidic group as the polar group are monomers having carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, ethylacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, fumaric acid, acryloyloxyethyl phthalate and acryloyloxy succinate; monomers having sulfonic acid group such as acrylic acid ethyl 2-sulfonate, methacrylic acid ethyl 2-sulfonate and butylacrylamido-sulfonic acid; monomers having phosphonic acid group such as methacrylic acid ethyl 2-phosphonate and acrylic acid ethyl 2-phosphonate; and monomers having hydroxyl group such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate. Preferred are monomers having carboxyl group or hydroxyl group.
Examples of monomers having basic group are monomers having primary amino group such as acrylic acid amide, aminoethyl acrylate, aminopropyl acrylate, methacrylic acid amide, aminoethyl methacrylate and aminopropyl methacrylate; monomers having secondary amino group such as methylaminoethyl acrylate, methylaminopropyl acrylate, ethylaminoethyl acrylate, ethylaminopropyl acrylate, methylaminoethyl methacrylate, methylaminopropyl methacrylate, ethylaminoethyl methacrylate and ethylaminopropyl methacrylate; monomers having tertiary amino group such as dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminopropyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminopropyl methacrylate and diethylaminopropyl methacrylate; and monomers having quaternary amino group such as acrylic acid dimethylaminoethylmethyl chloride, methacrylic acid dimethylaminoethylmethyl chloride, acrylic acid dimethylaminoethylbenzyl chloride and methacrylic acid dimethylaminoethylbenzyl chloride.
As the other polymerizable monomers, mention may be made of, for example, (meth)acrylates such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-propyl acrylate, n-butyl acrylate, t-butyl acrylate, benzyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, tridecyl methacrylate, benzyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, octyl acrylate, octyl methacrylate, lauryl acrylate, lauryl methacrylate, cetyl acrylate, cetyl methacrylate, stearyl acrylate, stearyl methacrylate, behenyl acrylate and behenyl methacrylate; styrene monomers such as styrene, xcex1-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene and p-tert-butylstyrene; itaconates such as benzyl itaconate; maleates such as dimethyl maleate; fumarates such as dimethyl fumarate; acrylonitrile, methacrylonitrile, vinyl acetate; hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate; amino group-containing monomers such as aminoethyl ethylacrylate, aminopropyl acrylate, methacrylic acid amide, aminoethyl methacrylate, aminopropyl methacrylate, dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate; and xcex1-olefins such as ethylene.
As the catalysts, mention may be made of, for example, known polymerization initiators, e.g., peroxides such as t-butylperoxy benzoate, di-t-butyl peroxide, cumene perhydroxide, acetyl peroxide, benzoyl peroxide and lauroyl peroxide; and azo compounds such as azobisisobutyronitrile, azobis-2, 4-dimethylvalero-nitrile and azobiscyclohexanecarbonitrile.
As the non-reactive solvents, mention may be made of, for example, aliphatic hydrocarbon solvents such as hexane and mineral spirit; aromatic hydrocarbon isolvents such as benzene, toluene and xylene; ester solvents such as butyl acetate; alcohol solvents such as methanol and butanol; ketone solvents such as methyl ethyl ketone and isobutyl methyl ketone; and non-protonic polar solvents such as dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone and pyridine. These solvents may be used in combination.
The reaction methods include generally known methods such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization and redox polymerization. Of these methods, solution polymerization is preferred because this method is simple.
The reaction conditions vary depending on the polymerization initiator and solvent used, but the reaction temperature is not higher than 180xc2x0 C., preferably 30-150xc2x0 C., and the reaction time is from 30 minutes to 40 hours, preferably from 2 hours to 30 hours.
As mentioned above, according to the present invention, the graft copolymer A is adsorbed to the particulate material, whereby the particulate material is finely dispersed and dispersion stabilized, and electric charge is given to the particulate material. From the point of dispersion stability for various solvents, when the graft copolymer is crosslinked and is adsorbed to the particulate material, the dispersion stability can be further improved.
The kind of linkage in crosslinking is not especially limited and includes ester linkage, amino linkage, urethane linkage, ether linkage and Cxe2x80x94C linkage formed by radical reaction. The ester linkage and amino linkage are especially preferred from the points of reaction rate, reaction time and stability at dispersion of the particulate material.
Method for crosslinking the graft copolymer A includes a method of using crosslinking agents and a method of introducing a functional group for crosslinking into the graft copolymer A.
The crosslinking agents are not limited as far as they can react with the polar group in the graft copolymer A, and examples thereof are amino resins such as melamine resins, benzoguanamine resins and urea resins; isocyanate resins such as tolylene diisocyanate prepolymers, polyfunctional aromatic polyisocyanates, diphenylmethane diisocyanate, hexamethylene diisocyanate prepolymers, xylylene isocyanate prepolymers and lysine isocyanate prepolymers; epoxy resins such as bisphenol A and acrylic resins having glycidyl group; and chelate compounds of Ti, Al, Zr or the like. Among them, amino resins and epoxy resins are especially preferred from the points of reaction rate and reaction temperature. Since silicone acrylic copolymers have only one kind of functional group, crosslinking agents are sometimes needed.
The functional groups for crosslinking introduced into the graft copolymer A include amino group, hydroxyl group, methoxy group, glycidyl group and the like. Among them, hydroxyl group and glycidyl group are especially preferred from the points of reaction rate and reaction temperature.
As the method for introducing the functional group for crosslinking, generally known ones can be employed. For example, there are a method of carrying out polymerization or condensation using monomers having the functional group for crosslinking, polyhydric alcohol and hydroxylamine or polyamine at the time of preparation of the graft copolymer A having acidic group and a method of introducing the crosslinking functional group by polymerization, condensation or addition reaction after preparation of a prepolymer of the graft copolymer A having acidic group. It is needless to say that after the introduction of the functional group for crosslinking, the graft copolymer A is adsorbed to the particulate material.
Examples of the monomers having the functional group for crosslinking used in preparation of the graft copolymer A are hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, glycerol monomethacrylate, polyethylene glycol monomethacrylate, propylene glycol monomethacrylate, polyethylene glycol monoacrylate and propylene glycol monoacrylate; glycidyl group-containing monomers such as glycidyl acrylate and glycidyl methacrylate; methoxy group-containing monomers such as methoxypolyethylene glycol and methoxypolyethylene glycol methacrylate; and amino group-containing monomers such as acrylamide and methacrylamide. Among them, glycidyl group-containing monomers are preferred since hydroxyl group is produced after the reaction to improve the electric charge of the particulate material.
Furthermore, in the method of introducing the functional group for crosslinking by polymerization, condensation or addition reaction after preparation of the prepolymer of the graft copolymer A, compounds having the crosslinking functional group for introduction by polymerization, condensation or addition reaction are not limited as far as they have two or more reactive groups, and examples of the compounds are polyhydric alcohols, polyamines, hydroxyamines, bisphenol A and polyisocyanates.
The particulate materials are not limited as far as they are insoluble in organic solvents, and examples of the particulate materials are inorganic pigments, organic pigments, dyes insoluble in solvents, fillers, medicines, polymerization initiators, catalysts, and ultraviolet absorbers.
Examples of the inorganic pigments are carbon black, titanium oxide, zinc white, zinc oxide, tripone, iron oxide, aluminum oxide, silicon dioxide, kaolinite, montmorillonite, talc, barium sulfate, calcium carbonate, silica, alumina, cadmium red, red iron oxide, molybdenum red, chrome vermilion, molybdate orange, chrome yellow, cadmium yellow, yellow iron oxide, titan yellow, chromium oxide, viridian, cobalt green, titan cobalt green, cobalt chrome green, ultramarine, ultramarine blue, prussian blue, cobalt blue, cerulean blue, manganese violet, cobalt violet and mica.
Examples of the organic pigments are azo, azomethine, polyazo, phthalocyanine, quinacridone, anthraquinone, indigo, thioindigo, quinophthalone, benzimidazolone, isoindoline and isoindolinone pigments.
Examples of the dyes insoluble in solvents are azo, anthraquinone, indigo, phthalocyanine, carbonyl, quinonimine, methine, quinoline and nitro dyes. Among them, disperse dyes are especially preferred.
In the dispersion composition of the present invention, amount of the graft copolymer A adsorbed to the particulate material is not limited, but is preferably in the range of 20-3000 parts by weight based on 100 parts by weight of the particulate material. If the amount of the graft copolymer A is less than 20 parts by weight, dispersion stability is lost, and if it exceeds 3000 parts by weight, content of the particulate material in the dispersion composition decreases and it becomes difficult to obtain a concentration of the particulate material sufficient for utilizing as ink, toner, etc. In the dispersion composition of the present invention, more preferred range of the amount of the graft copolymer A for the particulate material is 30-1000 parts by weight based on 100 parts by weight of the particulate material.
Exact mechanism of adsorption of the graft copolymer A to the particulate material has not yet been elucidated. It is supposed that the graft copolymer A is adsorbed to the surface of the particulate material by one of or combination of the following manners: chemical bonding (for example, an acid-base bonding such as bonding between basic site on the surface of the particulate material and acidic site of the graft copolymer A caused by deviation of electrons or between a tertiary amino group introduced onto the surface of the particulate material and a carboxyl group introduced into the graft copolymer A, ionic bonding caused by formation of salt by a metal ion of bivalence or higher valence and the graft copolymer A, covalent bonding caused by polymerization based on the active group on the surface of the particulate material, and the like), physical adsorption (for example, adsorption caused by agglomeration force of the graft copolymer A becoming insoluble in solvent to result in agglomeration, mechanical adsorption caused by dispersing the particulate material and the graft copolymer A by a dispersing machine, and the like) or physico-chemical adsorption (for example, caused by dispersing the graft copolymer A and the particulate material and reacting the active group on the surface of the particulate material with the graft copolymer A while adsorbing the graft copolymer A to the surface of the particulate material, and the like).
The amount of the graft copolymer A adsorbed to the particulate material can be measured by generally known method. For example, it can be indirectly measured by adjusting the concentration of nonvolatile matter to a given concentration, then subjecting the dispersion composition to centrifugal separation until the supernatant liquid becomes transparent, and measuring the concentration of the graft copolymer A in the supernatant liquid.
The organic solvents usable in the dispersion composition of the present invention are not limited, but are preferably those which are small in polarity and have a resistivity of not less than 109 xcexa9xc2x7cm. The organic solvents suitable for such purpose include, for example, aliphatic hydrocarbon solvents such as hexane and mineral spirit; silicone oils such as dialkylpolysiloxanes and cyclic polydialkylsiloxane; vegetable oils such as olive oil, safflower oil, sunflower oil, soybean oil and linseed oil; aromatic hydrocarbon m solvents such as benzene, toluene and xylene; ester solvents such as butyl acetate; alcohol solvents such as methanol and butanol; ketone solvents such as methyl ethyl ketone and isobutyl methyl ketone; and non-protonic polar solvents such as dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone and pyridine. These solvents may be used each alone or in combination of two or more. Of these solvents, considering generation of electric charge, preferred are, for example, aliphatic hydrocarbons such as hexane, mineral spirit and Isopar series manufactured by Exone Chemical Co., Ltd., silicone oils such as dialkylpolysiloxanes and cyclic polydialkylsiloxanes; and vegetable oils such as olive oil, safflower oil, sunflower oil, soybean oil and linseed oil, and more preferred are non-protonic organic solvents which are non-polar organic solvents having a resistivity of not less than 109 xcexa9xc2x7cm (e.g., aliphatic hydrocarbons and silicone oils).
Proportion of the organic solvents is preferably 50-10000 parts by weight, more preferably 100-3000 parts by weight based on 100 parts by weight of the particulate material. The dispersion composition of the present invention may additionally contain surface active agents, preservatives, deodorants, anti-skinning agents, perfumes, pigment dispersants, pigment derivatives, and the like.
The dispersion composition of the present invention can be produced, for example, by mixing a dispersion prepared by dispersing the particulate material using the graft copolymer A in an organic solvent in which the graft copolymer A is soluble with an organic solvent in which the graft copolymer A is insoluble, whereby the graft copolymer A is precipitated and adsorbed to the particulate material.
In more detail, the production method of the dispersion composition comprises a dispersing step A where the particulate material is dispersed using the graft copolymer A in an organic solvent in which the graft copolymer A is soluble, a mixing step B where an organic solvent in which the graft copolymer A is insoluble is poured into the dispersion obtained in the dispersing step A or the dispersion obtained in the dispersing step A is poured into an organic solvent in which the graft copolymer A is insoluble, followed by mixing them to precipitate the graft copolymer A and to adsorb the graft copolymer to the particulate material, an optional crosslinking step C where the graft copolymer A is fixed by crosslinking, and an optional concentrating step D where the solvent is distilled off.
In the dispersing step A, the graft copolymer A is dissolved in the organic solvent and the particulate material is added thereto and, if necessary, dispersing is carried out using a dispersing medium such as glass beads, steel beads or zirconia beads and by a dispersing machine, e.g., beads mill such as dynomill or DSP mill, roll mill, sand mill, attritor, kneader or a high-pressure jetting mill such as nanomizer, thereby obtaining a dispersion. Furthermore, if necessary, to the dispersion, there may be added various additives such as surface active agents, pigment dispersants, pigment derivatives, and charge generators.
The conditions for dispersing by dispersing machines vary depending on the kind of the particulate material or the kind of dispersing machines, but from economical viewpoint, the temperature is preferably 0-150xc2x0 C., and the dispersing time is preferably as shorter as possible, but 0.1-10 hours/kg is preferred from the point of productivity. Dispersion particle diameter after performing the dispersing is preferably smaller than that of submicron particles, and more preferably not more than 0.5 micron considering sedimentation and agglomeration.
The measuring method is not limited and generally employed methods are utilized. For example, there may be used particle size distribution meter of laser scattering type or centrifugal settling type. Moreover, the crosslinking agent for crosslinking the graft copolymer A is added before or after the dispersing. It is especially preferred to add it after the dispersing because of less influence on reaction or the like at the time of dispersing. Amount of the crosslinking agent is not limited as far as the graft copolymer A can be crosslinked and fixed on the particulate material, but is preferably 2-100 parts by weight, more preferably 5-50 parts by weight based on 100 parts by weight of the graft copolymer A.
In the next mixing step B, the organic solvent in which the graft copolymer A is insoluble is slowly added to the dispersion prepared in the dispersing step A or the dispersion obtained in the dispersing step A is slowly added to the organic solvent in which the graft copolymer A is insoluble, followed by mixing them. In this case, at the time of addition or after addition, the dispersion is uniformly mixed using a simple stirrer such as three-one motor, magnetic stirrer, disper or homogenizer. Furthermore, the organic solvent in which the graft copolymer A is insoluble and the dispersion prepared in the dispersing step A are mixed at one time using a mixing machine such as a line mixer. After addition, a dispersing machine such as a beads mill or a high-pressure jetting mill may be employed for the purpose of making finer the precipitated particles.
The organic solvents in which the graft copolymer A is insoluble are not limited as far as the graft copolymer A does not dissolve therein, but especially preferred are those having a solubility parameter of not more than 7.8. Examples of the organic solvents having a solubility parameter of not more than 7.8 are aliphatic hydrocarbons such as hexane, mineral spirit and Isopar series manufactured by Exone Chemical Co., Ltd., silicones such as dialkylpolysiloxanes and cyclic polydialkylsiloxanes, vegetable oils such as olive oil, safflower oil, sunflower oil, soybean oil and linseed oil, and diethyl ether. Amount of the organic solvents used here is preferably 0-10000 parts by weight based on 100 parts by weight of the graft copolymer A for increasing the concentration of the particulate material in the resulting dispersion composition.
In the crosslinking step C of fixing the graft copolymer A by crosslinking, the crosslinking method is not limited, and examples are heating, and irradiation with ultraviolet rays or electron rays. Especially, heating is preferred from the points of reactivity and simple reaction apparatus used. The temperature for crosslinking by heating is not limited so long as the dispersion state of the particulate material is not broken, but is preferably not higher than 200xc2x0 C., more preferably not higher than 180xc2x0 C.
The concentrating step D is carried out depending on use of the particulate material. Moreover, the concentrating step may be carried out before the crosslinking step C. For the concentration of the solvent, general atmospheric or vacuum distillation can be employed. For example, in the case of utilizing the dispersion composition with silicone solvent, an organic solvent having a boiling point lower than that of the silicone solvent is used as the organic solvent dissolving the graft copolymer A, and concentration is carried out by atmospheric distillation. On the other hand, in the case of utilizing the dispersion composition with the organic solvent dissolving the graft copolymer A, a silicone solvent having a boiling point lower than that of the organic solvent dissolving the graft copolymer A is used, and concentration is carried out by atmospheric distillation. Furthermore, if necessary, the solvent is completely distilled off or replaced with water, followed by drying, and the resulting dispersion composition can be utilized as powdered paints, toners, plastics and others.
The use of this dispersion composition is not limited, and examples thereof are paints for automobiles, constructions and PCM, printing inks such as gravure inks, inks for ink jet printers, liquid toners for wet electrophotographic printing machines or ink jet printers utilizing electrostatic force (disclosed, for example, in JP-A-8-291267, Japanese Patent No.2735030, and xe2x80x9cHigh-concentration ink jet recordingxe2x80x9d in FALL Meeting of JHC ""98). Particularly, in the field of liquid toners, the toners are excellent in long-term use stability since no special charge generating agent is needed and, besides, the electric charge is stably fixed on the surface of the particulate material.
In using the dispersion composition of the present invention for these uses, the composition is adjusted to a given concentration of particulate material or a given binder concentration by adding a binder, an organic solvent and various additives depending on the use. As the binder, there may be used generally known ones, for example, natural protein, celluloses, synthetic polymers such as polyvinyl alcohol, polyacrylamide, aromatic amides, polyacrylic acids, polyvinyl ether, polyvinyl pyrrolidone, acrylic resins, polyester resins, alkyd resins, urethane resins, amide resins, melamine resins, ether resins, fluorocarbon resins, styrene-acrylic resins, and styrene-maleic acid resins, photosensitive resins, thermosetting resins, ultraviolet-curing resins or electron ray-curing resins. The binders are not limited to these examples.
The various additives include generally known additives, e.g., anionic, cationic and nonionic surface active agents, anti-skinning agents, leveling agents, electric charge adjusting agents such as metallic soaps and lecithin, and wetting agents. These are not limiting.
Preparation of final paints, printing inks or wet toners by adding the above binders, organic solvents and various additives to the dispersion composition of the present invention can be performed by using a simple stirrer such as disper, and dispersing machines and others which are conventionally needed are not necessary and thus production with energy-saving and at low cost becomes possible.